J. Obstet. Gynaecol. Res. Vol. 31, No. 2: 94 – 97, April 2005 94 Blackwell Science, LtdOxford, UKJOGThe Journal of Obstetrics and Gynaecology Research1341-80762005 Asia and Oceania Federation of Obstetrics and GynaecologyApril 20053129497Original Article Treatment of SVT in twinsS. Tanawattanacharoen et al. Received: September 19 2003. Accepted: November 15 2004. Reprint request to: Dr Somchai Tanawattanacharoen, Department of Obstetrics and Gynecology, Faculty of Medicine, Chulalongkorn University, Rama IV Road, Bangkok 10330, Thailand. Email: fmedstn@md2.md.chula.ac.th Intrauterine therapy for fetal supraventricular tachycardia in a twin pregnancy Somchai Tanawattanacharoen 1 , Boonchai Uerpairojkit 1 , Somchai Prechawat 2 , Saknan Manotaya 1 and Dhiraphongs Charoenvidhya 1 Departments of 1 Obstetrics and Gynecology and 2 Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand Abstract A case of a twin pregnancy in which one fetus developed hydrops secondary to supraventricular tachycardia was detected at 21 weeks’ gestation. Transplacental digoxin therapy successfully converted the supraventric- ular tachycardia to a normal sinus rhythm without evidence of maternal or fetal side-effects. The pregnancy proceeded to term and elective cesarean section was carried out at 37 weeks’ gestation. Key words: anti-arrhythmic drug, digoxin, hydrops fetalis, supraventricular tachycardia, twin pregnancy. Introduction Although cardiac arrhythmias are detected in approx- imately 1% of all fetuses, the majority of these rhythm disturbances are the result of extrasystoles and are of little clinical significance. 1 However, sustained fetal supraventricular tachycardia (SVT) over a critical heart rate of approximately 210 b.p.m. can result in the development of congestive heart failure. 2 It has long been advocated that the fetus with SVT and hemody- namic compromise requires active intervention with medical therapy or delivery, depending on the gesta- tional age. Digoxin has been widely accepted as a first- line treatment, 3,4 although is associated with poor response rates, particularly in the setting of hydrops. Flecainide has recently become a more common choice due to its excellent maternal and fetal bioavailability, 4,5 but concerns about potentially significant side-effects have limited its use. 6,7 Twin pregnancy is associated with significantly increased and more severe obstetric complications. Management of these complications needs modifica- tion to account for the risks of the mother and each individual fetus. In this report, we present a single fetal hydrops secondary to SVT in the setting of a twin pregnancy, and the successful intrauterine therapy. Case Report A 36-year-old woman, gravid 3 para 1, was referred for prenatal care because of a suspected monochorionic monoamnionic twin pregnancy. On ultrasound exam- ination at 20 weeks, a single placenta with a thin intertwin septum (1.2 mm) was identified and mono- chorionic diamnionic twins was diagnosed. There was a 20% weight discordancy between the male fetuses (408 g and 324 g, respectively), but otherwise they were normal. The deepest vertical pockets of amniotic fluid in the bigger first twin’s and the smaller second twin’s sacs were 5.9 and 1.4 cm, respectively. Early twin–twin transfusion syndrome was suspected. Genetic amniocentesis was carried out in the first twin’s sac and cytogenetic analysis revealed a normal male karyotype (46,XY).